For many health conditions, an increased circumference of a patient's limb, torso, waistline, or other body portion is indicative of a negative health event. For example, a rapid increase in the circumference of a patient's leg is often due to edema—a swelling of the leg. Edema may be indicative of deep vein thrombosis, congestive heart failure, liver disease, kidney disease, an allergic reaction, inflammation caused by injury or infection, or other serious medical condition. Gradual increases in the circumference of a waistline or other body portion may be due to weight gain, which itself may be indicative of inactivity, overeating, depression, a hormonal imbalance, or other medically-relevant condition. On the other hand, for some individuals, such as those being treated for cancer, pregnant women, undernourished individuals, and athletes, a gradual increase in the circumference of a body portion may be desirable, and may be indicative of healthy weight gain, a growing fetus, or an increase in muscle mass. In each of the above scenarios, monitoring the circumference of a body portion may provide valuable insights into the health or wellness of an individual.
Early detection of circumferential changes of the body is crucial for some conditions such as deep vein thrombosis (DVT). DVT is characterized by the formation of a blood clot in a deep vein of a patient, typically in a patient's leg. Venous insufficiency and subsequent formation of a blood clot may cause considerable swelling, pain, redness, and increased body temperature near the clot. Additionally, patients with DVT are at risk of developing a pulmonary embolism (PE). PE can be a life-threatening complication, which occurs when a blood clot in a deep vein breaks loose, travels to the lungs, and blocks an artery in the lungs. It is estimated that 10-30% of patients die from DVT/PE within a month of diagnosis. In the United States of America, DVT/PE is estimated to cause 60,000-100,000 deaths each year. However, if the blood clot is identified early, when it is still developing in a deep vein, DVT can often be treated effectively with pharmaceutical agents designed to prevent the clot from growing or detaching and traveling to the lungs. If identified early, patients can also reduce the likelihood of clot growth and detachment through exercise. Accordingly, there is a critical need for early detection of DVT. Currently, detection means are lacking outside the clinical setting.
Certain risk factors greatly increase an individual's likelihood of developing DVT. For example, there is an increased prevalence of DVT in individuals whose limbs are immobile or inactive for long periods of time due to recovery after orthopedic surgery or other surgery, hospitalization, bed rest, or long-distance travel by airplane or automobile. Pregnancy, leg injuries, some prescription drugs, and some cancers are also known to increase a person's risk of developing DVT. The risk may be lowered through actions such as exercising, elevating the legs, abstaining from smoking, surgery, and taking a blood thinner or other pharmaceutical agent. Due to the importance of prevention and early detection of DVT, there is a need to monitor at risk individuals and encourage them to engage in activities and habits that lower their risk of developing pre-DVT conditions such as edema or DVT itself.